The main purpose of this Thematic Unit is to familiarize students with the stages of conducting research in the social sciences (with particular emphasis on the police studies and criminal justice), as well as to develop critical ability towards research results in these scientific fields. More specifically, it is expected that students will understand the basic principles governing scientific research and will acquire the necessary knowledge and skills required for the design of a scientific research (specialization of a research topic, placement of research questions, methodology design, presentation of results and drawing valid conclusions). At the same time, students are expected to develop critical thinking towards research results and conclusions. Also, students will be introduced to contemporary issues related to quantitative research approaches, in order to help them expand both in the design and analysis of data with statistical techniques used to investigate issues related to criminal justice. This thematic unit focuses on the basic techniques of descriptive and inductive statistics, with emphasis on the understanding of techniques, the interpretation and presentation of results, and the analysis of empirical data using statistical packages. Also, in this thematic unit, reference is made to the philosophical background, on which qualitative research is based, coupled with the exposition of the most important techniques of qualitative research; that is, individual and group interview, observation, and analysis of texts.